#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main ()
{
	char input = 0;
	scanf("%c",&input);
	if(input>='A' && input<='Z' || input>='a' && input<='z')
	{
	    printf("YES");
	}
	else
	{
	    printf("NO");
	}
    return 0;
}